The present invention relates to energy storage systems and more particularly to a photochemical energy storage system capable of both converting optical energy to a highly stable form for storage and of drawing from the stored energy form upon demand.
It has been discovered that water can be photodissociated into hydrogen and oxygen at very low voltage potentials by using titanium dioxide electrodes and a light source which produces substantial amounts of radiation in the ultraviolet region of the spectrum. This discovery has opened a new area of research into the conversion of solar energy into hydrogen, which is a more usable and storable form of energy. The hydrogen generated by the photodissociation process can be stored for subsequent use either as a high pressure gas or as a metal hydride. However, the need to store and transport hydrogen gives rise to well-known hazards.
For this reason, efforts have been made to discover photochemical reactions which result in a stable, high energy storage product. The problem with known photochemical reactions is that the reverse reaction occurs rapidly when the application of input energy (for example, solar energy) is interrupted. During the reverse reaction, the stored energy is rapidly lost in the form of heat.
The problem is how to store the energy in a safe, stable form for later delivery at a controlled rate.